'\" et
.TH AIO_WRITE "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
aio_write
\(em asynchronous write to a file
.SH SYNOPSIS
.LP
.nf
#include <aio.h>
.P
int aio_write(struct aiocb *\fIaiocbp\fP);
.fi
.SH DESCRIPTION
The
\fIaio_write\fR()
function shall write \fIaiocbp\fP\->\fIaio_nbytes\fR to the file
associated with \fIaiocbp\fP\->\fIaio_fildes\fR from the buffer pointed
to by \fIaiocbp\fP\->\fIaio_buf\fR. The function shall return when
the write request has been initiated or, at a minimum, queued to the
file or device.
.P
If prioritized I/O is supported for this file, then the asynchronous
operation shall be submitted at a priority equal to a base scheduling
priority minus \fIaiocbp\fP\->\fIaio_reqprio\fR. If Thread Execution
Scheduling is not supported, then the base scheduling priority is that
of the calling process;
.br
otherwise, the base scheduling priority is that of the calling thread.
.P
The
.IR aiocbp
argument may be used as an argument to
\fIaio_error\fR()
and
\fIaio_return\fR()
in order to determine the error status and return status, respectively,
of the asynchronous operation while it is proceeding.
.P
The
.IR aiocbp
argument points to an
.BR aiocb
structure. If the buffer pointed to by \fIaiocbp\fP\->\fIaio_buf\fR or
the control block pointed to by
.IR aiocbp
becomes an illegal address prior to asynchronous I/O completion, then
the behavior is undefined.
.P
If O_APPEND is not set for the file descriptor
.IR aio_fildes ,
then the requested operation shall take place at the absolute
position in the file as given by
.IR aio_offset ,
as if
\fIlseek\fR()
were called immediately prior to the operation with an
.IR offset
equal to
.IR aio_offset
and a
.IR whence
equal to SEEK_SET.
If O_APPEND is set for the file descriptor, or if
.IR aio_fildes
is associated with a device that is incapable of seeking, write operations
append to the file in the same order as the calls were made, except
under circumstances described in
.IR "Section 2.8.2" ", " "Asynchronous I/O".
After a successful call to enqueue an asynchronous I/O operation, the
value of the file offset for the file is unspecified.
.P
The
.IR aio_sigevent
member specifies the notification which occurs when the request is
completed.
.P
The \fIaiocbp\fP\->\fIaio_lio_opcode\fR field shall be ignored by
\fIaio_write\fR().
.P
Simultaneous asynchronous operations using the same
.IR aiocbp
produce undefined results.
.P
If synchronized I/O is enabled on the file associated with
\fIaiocbp\fP\->\fIaio_fildes\fR, the behavior of this function shall
be according to the definitions of synchronized I/O data integrity
completion, and synchronized I/O file integrity completion.
.P
For any system action that changes the process memory space while an
asynchronous I/O is outstanding to the address range being changed, the
result of that action is undefined.
.P
For regular files, no data transfer shall occur past the offset maximum
established in the open file description associated with
\fIaiocbp\fP\->\fIaio_fildes\fR.
.SH "RETURN VALUE"
The
\fIaio_write\fR()
function shall return the value zero if the I/O operation is
successfully queued; otherwise, the function shall return the value
\-1 and set
.IR errno
to indicate the error.
.SH ERRORS
The
\fIaio_write\fR()
function shall fail if:
.TP
.BR EAGAIN
The requested asynchronous I/O operation was not queued due to system
resource limitations.
.P
Each of the following conditions may be detected synchronously at the
time of the call to
\fIaio_write\fR(),
or asynchronously. If any of the conditions below are detected
synchronously, the
\fIaio_write\fR()
function shall return \-1 and set
.IR errno
to the corresponding value. If any of the conditions below are detected
asynchronously, the return status of the asynchronous operation shall
be set to \-1, and the error status of the asynchronous operation
is set to the corresponding value.
.TP
.BR EBADF
The \fIaiocbp\fP\->\fIaio_fildes\fR argument is not a valid file
descriptor open for writing.
.TP
.BR EINVAL
The file offset value implied by \fIaiocbp\fP\->\fIaio_offset\fR would
be invalid,
.br
\fIaiocbp\fP\->\fIaio_reqprio\fR is not a valid value,
or \fIaiocbp\fP\->\fIaio_nbytes\fR is an invalid value.
.P
In the case that the
\fIaio_write\fR()
successfully queues the I/O operation, the return status of the
asynchronous operation shall be one of the values normally returned
by the
\fIwrite\fR()
function call. If the operation is successfully queued but is
subsequently canceled or encounters an error, the error status for the
asynchronous operation contains one of the values normally set by the
\fIwrite\fR()
function call, or one of the following:
.TP
.BR EBADF
The \fIaiocbp\fP\->\fIaio_fildes\fR argument is not a valid file
descriptor open for writing.
.TP
.BR EINVAL
The file offset value implied by \fIaiocbp\fP\->\fIaio_offset\fR would
be invalid.
.TP
.BR ECANCELED
The requested I/O was canceled before the I/O completed due to an
explicit
\fIaio_cancel\fR()
request.
.P
The following condition may be detected synchronously or asynchronously:
.TP
.BR EFBIG
The file is a regular file, \fIaiobcp\fP\->\fIaio_nbytes\fR is greater
than 0, and the starting offset in \fIaiobcp\fP\->\fIaio_offset\fR is
at or beyond the offset maximum in the open file description associated
with \fIaiocbp\fP\->\fIaio_fildes\fR.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.8.2" ", " "Asynchronous I/O",
.IR "\fIaio_cancel\fR\^(\|)",
.IR "\fIaio_error\fR\^(\|)",
.IR "\fIaio_read\fR\^(\|)",
.IR "\fIaio_return\fR\^(\|)",
.IR "\fIclose\fR\^(\|)",
.IR "\fIexec\fR\^",
.IR "\fIexit\fR\^(\|)",
.IR "\fIfork\fR\^(\|)",
.IR "\fIlio_listio\fR\^(\|)",
.IR "\fIlseek\fR\^(\|)",
.IR "\fIwrite\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<aio.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
